U.S. patent application number 13/082825 was filed with the patent office on 2012-07-05 for magnetoresistance sensor and fabricating method thereof.
This patent application is currently assigned to VOLTAFIELD TECHNOLOGY CORPORATION. Invention is credited to Chien-Min Lee, FU-TAI LIOU.
Application Number | 20120169330 13/082825 |
Document ID | / |
Family ID | 46350760 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120169330 |
Kind Code |
A1 |
LIOU; FU-TAI ; et
al. |
July 5, 2012 |
MAGNETORESISTANCE SENSOR AND FABRICATING METHOD THEREOF
Abstract
An apparatus of a magnetoresistance sensor consisting of a
substrate, a conductive unit on the substrate, and a
magnetoresistance structure on the conductive unit is provided. The
conductive unit includes a first surface and a second surface
opposite to each other, and the first surface faces the substrate.
The magnetoresistance structure is formed on the second surface of
the conductive unit and is electrically connected to the conductive
unit. The magnetoresistance sensor has high performance and
reliability. A magnetoresistance sensor fabricating method based on
this apparatus is also provided.
Inventors: |
LIOU; FU-TAI; (Zhubei City,
TW) ; Lee; Chien-Min; (Zhudong Township, TW) |
Assignee: |
VOLTAFIELD TECHNOLOGY
CORPORATION
Hsinchu County
TW
|
Family ID: |
46350760 |
Appl. No.: |
13/082825 |
Filed: |
April 8, 2011 |
Current U.S.
Class: |
324/252 ; 29/846;
29/852 |
Current CPC
Class: |
G01D 5/16 20130101; Y10T
29/49165 20150115; G01R 33/09 20130101; B82Y 25/00 20130101; Y10T
29/49155 20150115; G01R 33/093 20130101; G01R 33/06 20130101 |
Class at
Publication: |
324/252 ; 29/846;
29/852 |
International
Class: |
G01R 33/02 20060101
G01R033/02; H05K 3/42 20060101 H05K003/42; H05K 3/46 20060101
H05K003/46 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 31, 2010 |
TW |
099147343 |
Claims
1. A magnetoresistance sensor, comprising: a substrate; a
conductive unit, configured on the substrate, the conductive unit
layer comprising a plurality of routing conductive traces and
having a first surface and a second surface on an opposite side of
the conductive unit to the first surface, the first surface facing
the substrate; and a magnetoresistance structure, configured on the
second surface of the conductive unit and electrically connected to
the conductive unit.
2. The magnetoresistance sensor of claim 1, wherein the conductive
unit further comprises: a first dielectric layer, configured on the
substrate; and a first conductive layer, configured in the first
dielectric layer and electrically connected to the
magnetoresistance structure, the first conductive layer
constituting the routing conductive traces.
3. The magnetoresistance sensor of claim 1, wherein the conductive
unit further comprises: a second dielectric layer, formed on the
substrate; a second conductive layer, configured in the second
dielectric layer; a first dielectric layer, formed on the second
conductive layer; a first conductive layer, configured in the first
dielectric layer, the first conductive layer and the second
conductive layer constituting the routing conductive traces; and a
via contact, configured in the first dielectric layer and
electrically connected to the first conductive layer and the second
conductive layer.
4. The magnetoresistance sensor of claim 3, wherein a material of
the first conductive layer is either tungsten or copper formed by
using a single or dual damascene process, and a material of the
second conductive layer is either aluminum or copper.
5. The magnetoresistance sensor of claim 3, wherein the first
dielectric layer and second dielectric layer are made of a
dielectric material of either silicon oxide or silicon nitride.
6. The magnetoresistance sensor of claim 1, wherein the substrate
is a silicon substrate covered by a dielectric material or a
silicon chip having previously formed logic circuits.
7. The magnetoresistance sensor of claim 1, wherein the conductive
unit comprises the uppermost conductive layer.
8. The magnetoresistance sensor of claim 1, wherein the
magnetoresistance structure comprises: a magnetoresistance layer,
configured on the second surface of the conductive unit; and a hard
mask layer, configured on a surface of the magnetoresistance
layer.
9. The magnetoresistance sensor of claim 8, wherein the
magnetoresistance structure is based on the mechanism selected from
a group consisting of anisotropic magnetoresistance, giant
magnetoresistance, tunneling magnetoresistance, and combination
thereof.
10. The magnetoresistance sensor of claim 8, wherein a resistance
of the magnetoresistance layer changes due to an external magnetic
field variation, and a material of the magnetoresistance layer is
selected from a group consisting of ferromagnets, antiferromagnets,
paramagnetic or diamagnetic metals, tunneling oxides and
combination thereof.
11. The magnetoresistance sensor of claim 8, wherein a material of
the hard mask layer is selected from a group consisting of
conductors, semiconductors, non-conductors, and combination
thereof.
12. A fabricating method of a magnetoresistance sensor, comprising:
providing a substrate; forming a conductive unit on the substrate,
the conductive unit comprising a plurality of routing conductive
traces and having a first surface and a second surface on an
opposite side of the conductive unit to the first surface, the
first surface facing the substrate; and forming a magnetoresistance
structure on the second surface of the conductive unit to
electrically connect to the conductive unit.
13. The fabricating method of the magnetoresistance sensor of claim
12, wherein forming the conductive unit comprises: forming a first
dielectric layer on the substrate; and forming a first conductive
layer in the first dielectric layer to electrically connect to the
magnetoresistance structure, the first conductive layer
constituting the routing conductive traces.
14. The fabricating method of the magnetoresistance sensor of claim
12, wherein forming the conductive unit layer comprises: forming a
second dielectric layer on the substrate; forming a second
conductive layer in the second dielectric layer; forming a first
dielectric layer on the second conductive layer; forming a first
conductive layer in the first dielectric layer, the first
conductive layer and the second conductive layer constituting the
routing conductive traces; and forming a via contact in the first
dielectric layer to electrically connect to the first conductive
layer and the second conductive layer.
15. The fabricating method of the magnetoresistance sensor of claim
14, wherein a material of the first conductive layer is either
tungsten or copper formed by using a single or dual damascene
process, and a material of the second conductive layer is either
aluminum or copper.
16. The fabricating method of the magnetoresistance sensor of claim
14, wherein the first dielectric layer and second dielectric layer
are made of a dielectric material of either silicon oxide or
silicon nitride.
17. The fabricating method of the magnetoresistance sensor of claim
14, wherein a material of the via contact is either tungsten or
copper.
18. The fabricating method of the magnetoresistance sensor of claim
14, wherein forming the first conductive layer and the via contact
comprises a dual damascene process comprising the steps of:
defining a via hole and a trench in the first dielectric layer;
forming a barrier layer on surfaces of the through hole and the
trench; filling the via hole and the trench with a conductive
material to form the via contact and the first conductive layer;
and performing a planarization of the surfaces of the first
dielectric layer and the first conductive layer.
19. The fabricating method of the magnetoresistance sensor of claim
12, wherein the substrate is a silicon substrate covered by a
dielectric material or a silicon chip having previously formed
logic circuits.
20. The fabricating method of the magnetoresistance sensor of claim
12, wherein the conductive unit comprises the uppermost conductive
layer.
21. The fabricating method of a magnetoresistance sensor of claim
12, further comprising performing a planarization of the second
surface of the conductive unit before forming the magnetoresistance
structure.
22. The fabricating method of the magnetoresistance sensor of claim
12, wherein forming the magnetoresistance structure comprises:
forming a hard mask layer on a surface of the magnetoresistance
layer; and forming a magnetoresistance layer on the second surface
of the conductive unit.
23. The fabricating method of the magnetoresistance sensor of claim
22, wherein the magnetoresistance structure is based on the
mechanism selected from a group consisting of anisotropic
magnetoresistance, giant magnetoresistance, tunneling
magnetoresistance, and combination thereof.
24. The fabricating method of the magnetoresistance sensor of claim
22, wherein a resistance of the magnetoresistance layer changes due
to the external magnetic field variation, and a material of the
magnetoresistance layer is selected from a group consisting of
ferromagnets, antiferromagnets, paramagnetic or diamagnetic metals,
tunneling oxides and combination thereof.
25. The fabricating method of the magnetoresistance sensor of claim
20, wherein a material of the hard mask layer is selected from a
group consisting of conductors, semiconductors, non-conductors, and
combination thereof.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a magnetoresistance sensor
and a fabricating method thereof, and particularly to a
magnetoresistance sensor with high reliability and a fabricating
method thereof.
BACKGROUND OF THE INVENTION
[0002] With the development of consumer electronic products such as
mobile phones and electronic compasses, additionally together with
conventional products such as motors and brakes, the demand of
magnetoresistance sensors is progressively increasing.
[0003] Typically, a magnetoresistance sensor includes a substrate,
a magnetoresistance structure formed on the substrate and at least
one conductive layer formed on the magnetoresistance structure, and
in a conventional process for fabricating the magnetoresistance
sensor, the magnetoresistance structure is firstly formed prior to
the metallization process for forming the magnetoresistance
structure. Such processing sequence leaves a high risk of cross
contamination either to the backend equipments or front-end devices
(in the substrate) due to the outward diffusion of the magnetic
elements (for example iron, cobalt and nickel) in the
magnetoresistance structure. The other concern of the conventional
processes arises from thermal and stress accumulation contributed
from the subsequent metallization processes, such as forming the
conductive layer. The performance and reliability of the
magnetoresistance structure may also get worse under such
circumstances.
SUMMARY OF THE INVENTION
[0004] The present invention provides a magnetoresistance sensor
with excellent performance and high reliability.
[0005] The present invention also provides a fabricating method of
a magnetoresistance sensor, by which the performance and
reliability of the magnetoresistance sensor can be improved.
[0006] The present invention provides a magnetoresistance sensor,
which includes a substrate, a conductive unit and a
magnetoresistance structure. The conductive unit is configured on
the substrate. The conductive unit layer includes a plurality of
routing conductive traces, and has a first surface and a second
surface on an opposite side of the conductive layer to the first
surface. The first surface faces the substrate. The
magnetoresistance structure is configured on the second surface of
the conductive unit and electrically connected to the conductive
unit.
[0007] The present invention also provides a fabricating method of
a magnetoresistance sensor. The method includes providing a
substrate, forming a conductive unit on the substrate, and forming
a magnetoresistance structure on the conductive unit. The
conductive unit includes a plurality of routing conductive traces,
and has a first surface and a second surface on an opposite side of
the conductive unit to the first surface. The first surface faces
the substrate. The magnetoresistance structure is formed on the
second surface of the conductive unit, and is electrically
connected to the conductive unit.
[0008] In the magnetoresistance sensor of the present invention,
the magnetoresistance structure is formed after forming the
conductive unit. Following such sequence, the contamination risk to
backend equipments or front-end devices can be prevented, which is
due to the outward diffusion of magnetic elements such as iron,
cobalt and nickel used in the magnetoresistance structure.
Furthermore, the performance and reliability of the
magnetoresistance structures will not be deteriorated in the
absence of thermal cycles and stress accumulation induced in the
metallization process of forming the conductive unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The above objects and advantages of the present invention
will become more readily apparent to those ordinarily skilled in
the art after reviewing the following detailed description and
accompanying drawings, in which:
[0010] FIG. 1 is a cross-sectional, schematic view of a
magnetoresistance sensor in accordance with an embodiment of the
present invention;
[0011] FIG. 2 is a cross-sectional, schematic view of a
magnetoresistance sensor in accordance with another embodiment of
the present invention; and
[0012] FIG. 3 is a cross-sectional, schematic view illustrating a
partial process flow of a fabricating method of a magnetoresistance
sensor process in accordance with an embodiment of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] The present invention will now be described more
specifically with reference to the following embodiments. It is to
be noted that the following descriptions of preferred embodiments
of this invention are presented herein for purpose of illustration
and description only. It is not intended to be exhaustive or to be
limited to the precise form disclosed.
[0014] FIG. 1 is a cross-sectional, schematic view of a
magnetoresistance sensor in accordance with an embodiment of the
present invention. Referring to FIG. 1, a magnetoresistance sensor
200 includes a substrate 202, a conductive unit 232 and a
magnetoresistance structure 210. The substrate 202 can be either a
silicon substrate covered by a dielectric material or a silicon
chip having previously formed logic circuits. The conductive unit
232 is configured on the substrate 202. The conductive unit 232
includes a plurality of routing conductive traces, and has a first
dielectric layer 218 formed on the substrate 202 and a first
conductive layer 204 configured in the first dielectric layer 218.
In the present embodiment, the first conductive layer 204
constitutes the routing conductive traces. The first conductive
layer 204 is electrically connected to the magnetoresistance
structure 210. A material of the first conductive layer 204 can be
either tungsten or copper.
[0015] The conductive unit 232 has a first surface 212 and a second
surface 214 on an opposite side of the conductive unit 232 to the
first surface 212. The first surface 212 faces the substrate 202.
The magnetoresistance structure 210 is configured on the second
surface 214 of the conductive unit 232 and is electrically
connected to the conductive unit 232. In detail, the
magnetoresistance structure 210 includes a magnetoresistance layer
206 and a hard mask layer 208. The magnetoresistance layer 206 is
configured on the second surface 214 of the conductive unit 232,
and the hard mask layer 208 is configured on a surface of the
magnetoresistance layer 206. A passive protecting layer 226 is
formed on the hard mask layer 208 to protect the magnetoresistance
structure 210. Generally, the magnetoresistance layer 206 is based
on the mechanisms including anisotropic magnetoresistance (AMR),
giant magnetoresistance (GMR), tunneling magnetoresistance (TMR),
or combination thereof. A material of the magnetoresistance layer
206 can be, but not limited to, ferromagnets, antiferromagnets,
ferrimagnets, paramagnetic or diamagnetic metals, tunneling oxides,
or combination thereof.
[0016] In the present embodiment, after a general semiconductor
element or other circuit element (i.e. the conductive unit 232) is
formed on the substrate 202, the magnetoresistance structure 210 is
formed on the conductive unit 232. Therefore, the magnetic
materials such as iron, cobalt and nickel in the magnetoresistance
structure 210 will not contaminate the machines used in the
subsequent processes. Further, the thermal cycles and stress
accumulation in the subsequent metallization processes especially
lithography and etching will not affect the performance and
reliability of the magnetoresistance structure 210.
[0017] Additionally, in the present embodiment, the conductive unit
232 is configured on the substrate 202 and then the
magnetoresistance structure 210 is formed on the conductive unit
232. Here the hard mask layer 208 of the magnetoresistance
structure 210 is only used for defining the magnetoresistance layer
206 and does not serve as electrical contact to the conductive unit
232. Thus the hard mask layer 208 can be electrically conductive,
semi-conductive or non-conductive, and can be made of conductors,
semiconductors or non-conductors. Further, when the hard mask layer
208 is electrically conductive, taking the material of the hard
mask layer 208 is tantalum (Ta) or tantalum nitride (TaN) as an
example, it is not necessary for the hard mask layer 208 to have a
conventional function of preventing over-etching to the
magnetoresistance layer 206 during forming the conductive unit 232.
Therefore, a thickness of the conductive hard mask layer 208, for
example, can be decreased to be in a range from 100 to 150
angstroms (A). The thickness of the hard mask layer 208 is less
than the thickness of the hard mask layer in the conventional
magnetoresistance structure, which is in a range from 300 to 400
angstroms. In addition, the resistance of the hard mask layer 208
can also be higher than the resistance of the magnetoresistance
layer 206. Less hard mask thickness results in higher resistance,
which helps to reduce current shunting effect through the hard mask
layer 208 and therefore improves the magnetoresistance ratio.
Accordingly, the magnetoresistance layer 206 cooperated with the
thinner hard mask layer 208, can improve the sensitivity of
magnetic field detection.
[0018] In the following embodiments, the material, structure, and
process of elements having same reference numerals are identical or
similar to that of the aforementioned embodiment, and will not be
described here.
[0019] FIG. 2 is a cross-sectional, schematic view of a
magnetoresistance sensor in accordance with another embodiment of
the present invention. Referring to FIG. 2, in the present
embodiment, to improve the functionality of the magnetoresistance
sensor, a magnetoresistance sensor 300 includes a number of
conductive layers. The magnetoresistance sensor 300 includes a
substrate 202, a conductive unit 232, a magnetoresistance structure
210 and a via contact 220. The conductive unit 232 is configured on
the substrate 202. The conductive unit 232 includes a plurality of
routing conductive traces. In the present embodiment, the
conductive unit 232 includes a second dielectric layer 230 formed
on the substrate 202 and a second conductive layer 216 configured
in the second dielectric layer 230. Further, a first dielectric
layer 218 is formed on the second conductive layer 216, a first
conductive layer 204 is configured in the first dielectric layer
218. The via contact 220 is configured in the first dielectric
layer 218 and is electrically connected to the first conductive
layer 204 and the second conductive layer 216. In the present
embodiment, the first conductive layer 204 and the second
conductive layer 216 constitute the routing conductive traces. The
conductive unit 232 includes the uppermost conductive layer (i.e.,
the first conductive layer 204).
[0020] Usually, the first conductive layer 204 is configured for
sensing a resistance change of the magnetoresistance structure 210
in response to a magnetic field variation. The second conductive
layer 216 serves as a programming line and is configured for
changing or controlling the magnetization direction of the
magnetoresistance layer 206. The first dielectric layer 218 and the
second dielectric layer 230 can be a dielectric material of either
silicon dioxide or silicon nitride. A material of the first
conductive unit 204 can be either tungsten or copper, and a
material of the second conductive unit 216 can be either aluminum
or copper.
[0021] The conductive unit 232 has the first surface 212 and the
second surface 214 on an opposite side of the conductive unit 232
to the first surface 212. The first surface 212 faces the substrate
202. A magnetoresistance structure 210 is configured on the second
surface 214 of the conductive unit 232 and is electrically
connected to the conductive unit 232. The magnetoresistance
structure 210 includes a magnetoresistance layer 206 and a hard
mask layer 208. The hard mask layer 208 is configured on a surface
of the magnetoresistance layer 206 to define the magnetoresistance
layer 206, and is covered by a passive protecting layer 226 to
protect the magnetoresistance structure 210.
[0022] In the present embodiment, other conductive layers are not
disposed on the magnetoresistance structure 210, and two conductive
layers under the magnetoresistance structure 210 are illustrated as
an example. However, the number of the conductive layer is not
limited by the present embodiment. That is, more than two
conductive layers can be sequentially formed under the
magnetoresistance layer 206.
[0023] A fabricating method of the magnetoresistance sensors shown
in FIGS. 2, 3 is described as follows.
[0024] By using the fabricating method, the magnetic materials such
as iron, cobalt and nickel in the magnetoresistance structure 210
will not contaminate the machines used in the subsequent processes.
The performance and reliability of previously formed front-end
devices (i.e. logic circuits) will not be affected. Further, the
thermal cycles and stress accumulation in the subsequent
metallization processes especially lithography and etching will not
affect the performance and reliability of the magnetoresistance
structure 210. Referring to FIG. 2, in the present embodiment, the
substrate 202 is provided, and then the conductive unit 232 is
formed on the substrate 202. The step of forming the conductive
unit 232 includes forming the first dielectric layer 218 on the
substrate 202 and forming the first conductive layer 204 in the
first dielectric layer 218. The first conductive layer 204 is
configured for being electrically connected to the
magnetoresistance structure 210. The first dielectric layer 218 can
be a dielectric material such as silicon oxide or silicon nitride,
and the material of the first conductive layer 204 can be either
tungsten or copper.
[0025] The conductive unit 232 has the first surface 212 and the
second surface 214 on an opposite side of the conductive unit 232
to the first surface 212. The first surface 212 faces the substrate
202. The magnetoresistance structure 210 is formed on the second
surface 214 of the conductive unit 232, and is electrically
connected to the conductive unit 232. The step of forming the
magnetoresistance structure 210 includes forming the hard mask
layer 208 on the surface of the magnetoresistance layer 206, and
then forming the magnetoresistance layer 206 on the second surface
214 of the conductive unit 232. Before forming the
magnetoresistance structure 210, a planarization step of the second
surface 214 of the conductive unit 232 can be performed. In
addition, the passive protecting layer 226 can be formed to cover
and protect the magnetoresistance structure 210. In general, the
magnetoresistance layer 206 is based on the mechanisms including
anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR),
tunneling magnetoresistance (TMR), or combination thereof. The
material of the magnetoresistance layer 206 can be, but not limited
to, ferromagnets, antiferromagnets, ferrimagnets, paramagnetic or
diamagnetic metals, tunneling oxides or combination thereof.
[0026] Additionally, in the present embodiment, after the
conductive unit 232 is firstly formed on the substrate 202, the
magnetoresistance structure 210 is formed on the conductive unit
layer 232. Here, the hard mask layer 208 in the magnetoresistance
structure 210 is only used for defining the magnetoresistance layer
206 and does not serve as electrical contact to the conductive unit
232. Thus the hard mask layer 208 can be electrically conductive,
semi-conductive or non-conductive. Besides, since the position of
conductive unit 232 has changed, the hard mask layer 208 no longer
serves as an etch-stop layer to prevent over-etching damage to the
magnetoresistance layer 206 when forming the conductive unit 232 in
the conventional process. Therefore, the thickness of the
conductive hard mask layer 208, taking the material thereof is
tantalum (Ta) or tantalum nitride (TaN) as an example, can be
decreased to be in a range from 100 to 150 angstroms (A). However,
a thickness of the hard mask layer in a conventional
magnetoresistance structure is in a range from 300 to 400
angstroms. The thickness of the hard mask layer 208 in the present
embodiment is less than the thickness of the hard mask layer in
conventional magnetoresistance structure. In addition, the
resistance of the hard mask layer 208 can also be higher than the
resistance of the magnetoresistance layer 206. It's because less
hard mask thickness results in higher resistance, which helps to
reduce current shunting effect through hard mask layer 208 and
therefore improves the magnetoresistance ratio. Accordingly, the
magnetoresistance layer 206 cooperated with the thinner hard mask
layer 208, can improve the sensitivity of magnetic field
detection.
[0027] Considering the functionality and controllability of the
magnetoresistance sensors, the magnetoresistance sensor 300 in
another embodiment of the present invention utilizes a number of
conductive layers. Referring to Fig.3, the second dielectric layer
230 is formed on the substrate 202, and the second conductive layer
216 is formed in the second dielectric layer 230. The material of
the second conductive layer 216 can be either aluminum or copper.
Depending on the used material, the sequence of forming the second
dielectric layer 230 and forming the second conductive layer 216
can be swapped. Afterwards, the first dielectric layer 218 is
formed on the second conductive layer 216. The first dielectric
layer 218 and the second dielectric layer 230 can be made of a
dielectric material such as silicon oxide or silicon nitride. The
first conductive layer 204 and the via contact 220 can be formed
together, for example, using a dual damascene process, or
separately using twice single damascene processes. In the dual
damascene process, the via contact 220 and the first conductive
layer 204 can be made of copper or tungsten. In the twice single
damascene processes, the via contact 220 can be a tungsten plug and
the first conductive layer 204 can be made of copper or tungsten.
The purpose of the damascene processes here is to provide a flat
and smooth surface to meet the demand of the subsequent formed
magnetoresistance layer 206. The flat surface helps to maintain the
uniform magnetic domain orientation of the magnetoresistance layer
and therefore improve the quality of the magnetoresistance
signals.
[0028] In the present embodiment, the first conductive layer 204
and the via contact 220 is made of copper and a fabricating process
is described as follows. Firstly, the first dielectric layer 218 is
etched so as to define at least one via hole 222 connecting the
first conductive layer 204 and the second conductive layer 216 in
the first dielectric layer 218. Next, the trench 228 above the via
hole 222 is defined. The trench 228 is configured for forming the
first conductive layer 204. The pattern of the trench 228 fully
encloses the pattern of the via hole 222. Next, a barrier layer 224
is formed on surfaces of the via hole 222 and the trench 228 by a
physical or chemical vapor deposition method. The barrier layer 224
can be made of either a tantalum nitride (TaN) layer or a titanium
nitride (TiN) layer.
[0029] After depositing the barrier layer 224, a thin and uniform
copper seed layer (not shown) is formed by a vapor deposition
method in the trench 228 and the via hole 222 so as to provide
nucleating sites for further copper growth. Thus, a mass of copper
can be deposited to fill into the via hole 222 and the trench 228
by using electrical plating process. As a result, the via contact
220 and the first conductive layer 204 are formed simultaneously.
The via contact 220 can be electrically connected to the first
conductive layer 204 and the second conductive layer 206. After
that, the redundant copper on the surface is removed using a
chemical-mechanical polishing process to achieve a planarization of
the second surface 214 of the conductive unit 232.
[0030] Thereafter, referring to FIG. 2, the magnetoresistance layer
206 is formed on the planarized second surface 214, using the hard
mask layer 208 above for patterning After forming the
magnetoresistance structure 210, the magnetoresistance structure
210 can be covered by the passive protecting layer 206 to protect
the magnetoresistance structure 210.
[0031] The advantage of using copper conductive layer is its low
electrical resistivity (.about.1.7 .mu..OMEGA.-cm), which is only
two thirds of that of aluminum (.about.2.8 .mu..OMEGA.-cm). Thus,
when copper conductive layer is used, the parasitic resistance due
to metal wiring can be reduced and therefore the signal from the
magnetoresistance layer can be improved. In addition, the copper
conductive layers have better durability against electromigration,
thereby reducing the probability of disconnection of conductive
traces and improving the reliability of the magnetoresistance
sensors.
[0032] In summary, after the conductive unit is configured on the
substrate, the magnetoresistance structure is formed on the
conductive unit in the present embodiment. Therefore, the hard mask
layer in the magnetoresistance structure is only used for defining
the magnetoresistance layer and can be either conductive,
semi-conductive or non-conductive. That is, it is not necessary for
the hard mask layer to serve as the etch-stop layer when etching
the conductive unit in the conventional process. Accordingly, the
thickness of the hard mask layer in the present embodiment can be
less than the thickness of the hard mask layer in the conventional
magnetoresistance structure, and the resistance of the hard mask
layer can also be much higher than the resistance of the
magnetoresistance layer. Higher resistance helps to reduce current
shunting effect through hard mask layer and therefore improves the
magnetoresistance ratio. As a result, the magnetoresistance layer
cooperated with the thinner hard mask layer can improve the
sensitivity of magnetic field detection.
[0033] Additionally, after the conductive unit is configured on the
substrate, the magnetoresistance structure is configured on the
conductive unit, the magnetic materials such as iron, cobalt and
nickel used in the magnetoresistance structure 210 will not
contaminate the machines used in the subsequent processes. The
performance and reliability of previously formed front-end devices
(i.e. logic circuits) will not be affected. Further, the thermal
cycles and stress accumulation in the subsequent metallization
processes especially lithography and etching will not affect the
performance and reliability of the magnetoresistance structure.
[0034] Further, in the present embodiment, the damascene process is
used to form the topmost conductive layer. The damascene process
provides a flat and smooth surface to meet the demand of subsequent
formed magnetoresistance structure. When copper conductive layer is
used, one advantage is enhancement of the magnetoresistance signal
due to less parasitic resistance. In addition, the copper
conductive layer has better durability against electromigration,
thereby reducing the probability of disconnection of conductive
traces and improving the reliability of the magnetoresistance
sensors.
[0035] While the invention has been described in terms of what is
presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention needs not be
limited to the disclosed embodiment. On the contrary, it is
intended to cover various modifications and similar arrangements
included within the spirit and scope of the appended claims which
are to be accorded with the broadest interpretation so as to
encompass all such modifications and similar structures.
* * * * *